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Surgery of the Canine Urethra
Symposium on Surgical Techniques in Small Animal P;actice
Surgery of the Canine Urethra S. Gary Brown, D.V.M.*
ANATOMY The urethra serves a dual role both as a conduit for urine from the bladder to the outside and as a purveyor of seminal fluids. The first segment of the urethra is the prostatic urethra. This is followed by the membranous or intrapelvic urethra which extends from the caudal end of the prostate to the bulb of the penis that is superior to the caudal pelvic symphisis. Third, the extrapelvic or cavernous urethra begins at the bulb of the penis and extends to its tip. The urethra is a highly distensible organ whose diameter is slightly variable throughout, except at the caudal os penis where the bony os limits the urethra's ability to expand. This is a common area for urethral calculi to lodge. The entire urethra is lined with transitional epithelium with the exception of a small amount near the tip of the penis. Urethral muscle is composed of an inner longitudinal layer of smooth muscle ~nd aN outer transverse layer of skeletal muscle that are separated dorsally by a longitudinal connective tissue raphe. The prostatic urethra is supplied by the prostatic branch of the urogenital artery. The membranous or intrapelvic urethra receives most of the supply from the smaller urethral arteries. The extrapelvic or penile urethra is supplied by the artery of the urethral bulb. Venous drainage of the urethra flows into the internal pudendal vein. Autonomic nerves from the pelvic plexus supply the smooth muscle of the urethra. Voluntary control of urethral muscle is mediated by the pudenal nerve. The female urethra traverses caudally from the neck of the bladder and enters the floor of the vagina just slightly caudal to the junction between the vaginal and vestibular floor. The urethra opens on the urethral tubercle just cranial to the lips of the vulva. *Surgeon: Berkeley Veterinary Medica]. Group, Berkeley, California; Clinical Assistant Professor, Department of Clinical Sciences. College of Veterinary Medicine, University of California at Davis Veterinary Clinics of North America- Vol. 5, No. 3, August 1975
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CONGENITAL ANOMALIES
These rare conditions can often be diagnosed by physical examination. Urethral duplications, atresia, and diverticula can occur however, and are best confirmed by contrast cystourethrography. Hypospadias and epispadias usually occur with other congenital malformations. In hypospadias, the urethral opening is anywhere on the ventral surface although it is usually on the penis or the ventral glans penis shaft. In epispadias, the urethral orifice is on the upper surface of the penis somewhere caudal to the tip. URETHRAL PROLAPSE
Prolapse of the penile urethra, an infrequent occurrence, usually requires surgical treatment. It occurs most often in young brachiocephalic dogs such as Boston terriers and English bulldogs. Prolonged sexual excitement (real or imagined), urethral infection, and congenital abnormalities are probably the cause of this condition, although the exact etiopathogenesis is not fully understood. The diagnosis is based on history and clinical signs. Excessive licking of the tip of the penis and preputial orifice with noticeable hemorrhage from the prepuce suggests the possibility of this lesion. This is confirmed by direct observation of the mucosa protruding from the tip of the penis. Although the color and size of the prolapse vary, the mucosa is usually brig~t red to purple and donut shaped as it pushes forth to extend beyond and around the tip of the penis. Surgical Treatment
Under general anesthesia with nitrous oxide- oxygen (2 to 1) in halothane- the dog is placed in dorsal recumbency. The prepuce and surrounding abdomen are clipped and prepared aseptically for surgery. The preputial diverticulum and penis are irrigated with an antiseptic solution prior to scrubbing and draping the operative area. When the prolapse is small, and is not grossly engorged with blood, a conservative repair is preferred. The penis is extended from the sheath and grasped between the thumb and forefinger. A well lubricated catheter of the largest diameter that will pass easily is introduced into the urethral orifice while reduction of the prolapse is attempted. If the prolapse has been reduced the catheter is then placed into the bladder and a purse-string suture of 3-0 or 4-0 nylon is placed around the tip of the penis. The catheter is then sutured to the prepuce to maintain its position in the urethra and bladder for five to seven days. In some dogs, it is wise to add an Elizabethan collar at this point whereas in others it is unnecessary.
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E
Figure 1.
Surgical correction of urethral prolapse.
If the prolapse is severe and obviously nonreducible, amputation of the diseased tissue in the prolapsed segment is preferred. As with the preparation previously described the penis is grasped and a well lubricated catheter is inserted through the urethra into the bladder. Four stay sutures are placed equidistant around the tip of the penis through the urethral mucosa to prevent the inner mucosa from retracting (Fig. 1). The prolapse is excised over the catheter as close to the penis as possible. Simple interrupted sutures of 4-0 to 5-0 chromic catgut are placed around the tip of the penis approximately 2 to 4 mm apart uniting the urethral mucosa to the cranial tip of the penis. The catheter is sutured to the prepuce to maintain its position for four days. Postoperative Care
A urinary antibiotic such as sulfisoxazole (Gantrisin), acetylsulfafurazole (Lipogantrisin), chloramphenicol (Chloromycetin), or· genta-
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micin (Gentocin) should be used to control infection. A tranquilizer such as acepromazine has been quite beneficial. Here again, an Elizabethan collar is helpful to prevent catheter removal and licking at the operative site. If possible the urinary catheter is drained through a long polyethylene tube into a clean bottle to prevent retrograde contamination.
Complications Self-mutilation can be controlled as previously mentioned and postoperative bleeding can usually be arrested with synthetic estrogens or tranquilizers.
ACUTE URETHRAL TRAUMA Etiology Acute urethral trauma is often the result of catheterization of a urethra already edematous from the presence of disease or more often urethral calculi. Urethral calculi themselves, in fact, cause urethral trauma. Direct injury may be either a sharp laceration or blunt injury causing bruising and edema of the urethra and surrounding tissues. Because of its tearing nature, biting injuries of the urethra damage the tissue more extensively than does a sharp laceration; bite wounds increase the possibility of infection. Surgical damage to the female urethra can occur during resection of a vaginal tumor or vaginal prolapse if the female urethra has not been catheterized. In the male, injury to the tip of the penis has been reported following sexual activity that has resulted in the prolapsed urethra. Fracture of the os penis with attendant urethral injury occurs rarely in the dog.
Diagnosis Diagnosis is generally based on history, physical examination, catheterization, and plain film plus contrast urethrography. All trauma patients with hematuria should have close inspection of urinary systems. Contrast cystourethrograms or intravenous pyelograms are invaluable.
Complications The traumatized or lacerated urethra can result in strictures and dysuria. Urethral dilatation and other secondary disease (retention uropathy) of the urinary system, cranial to the lesion, can also occur. Leakage through a rupture may cause infiltration of the surrounding tissues with urine that can then progress to secondary edema and swelling of the scrotum and the rear limbs. Chronic urine retention from strictures can result in urinary tract infection, crystal formation, and hydrodilatations. Complete retention from strictures and ruptures result in anuria and uremia.
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Treatment
Extrapelvic Urethra. Bruising of the urethra and periurethra can be seen as a segmental narrowing of the dye stream in a cystourethrogram. If the urethra is intact, the injury is treated conservatively with urinary antibiotics, hot packs, and tranquilizers. If the urethra is intact and the tissues in the area are markedly bruised, manual expression or placement of a urinary diversion catheter, sutured to the prepuce, may be necessary for several days. Lacerations of the external urethra should be surgically treated before the urine extravasates into the surrounding tissues and causes edema. The edges of the laceration are approximated with sutures over a previously passed transurethral Foley or Brunswick catheter of the largest size that can be comfortably passed by the os penis into the bladder. If the laceration has been sharp, producing minimal tissue damage, the edges are approximated with simple interrupted 4-0 chromic catgut placed 2 mm apart, leaving a gap of 2mm between the urethral wound edges. This method of edge approximation over a catheter has been used to circumvent an unacceptable number of strictures resulting from primary water tight closures. If the rupture has occurred in a urethra that is already edematous, possibly from calculi, it is probably better to do a permanent prescrotal urethrostomy first so that then one would be able to pass a slighty larger Foley catheter to do the previous repair of the external urethra. This permanent urethrostomy will then be useful for the passage of future small stones. Suturing the external part of the catheter to the prepuce and/or incorporating this into a body bandage will prevent the dog from removing the catheter. This catheter should rema~n in place for seven to ten days. These extra precautions are desirable since reinsertion of the catheter may disrupt the sutured area of the urethra. If one expects a more chronic catheterization for any reason the catheter can be placed through a prescrotal permanent urethrostomy and sutured to the skin. For example, in more severe injuries where a loss of urethral tissue is creating a large defect or other massive disruption to the urethra, a large Foley catheter is passed through the prescrotal urethrostomy past the injury and into the bladder. One inch is allowed to protrude and sutured into the skin edge. The torn edges are approximated over the catheter by simple interrupted sutures of 4-0 chromic catgut with a gap of 2 mm always being left. It the edges are approximated over a large defect, there should be no tension on the sutures. The catheter may remain in place for two to three weeks as long as urinary antibiotics are being administered. Bite wounds of the urethra may be treated in like fashion, remembering that extensive damage predisposes to infection and therefore the wound is closed over a Penrose drain. If gross infection is present the external wound is debrided if necessary and dressed with antibiot-
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ics for two days while urinary diversion is maintained through a catheter. The dressing may be sutured directly to the skin. After two days the urethra and granulating tissue are closed over the catheter as described using a Penrose drain. Some mucosal continuity is desired for healing. In experimental and clinical studies of the anterior urethra, it has been demonstrated that regeneration of the urethra, including the corpus and corpus spongiosum, is possible provided that the urethra does not have to bridge an area of complete excision. This is important to remember when chronic catheterization is used for urethral defects. A severed urethra should be repaired as soon as possible. The ends of the severed urethra are debrided l to 2 mm prior to the anastomosis. Stay sutures are placed 180 degrees apart to position the anastomosis. The anastomosis is then completed with six to eight interrupted sutures of 4-0 chromic catgut placed circumferentially to bring together the mucosal and muscularis layers. The bottom layer is closed first and the layer closest to the surgeon (outer) is closed last over a Foley urinary diversion catheter. This is left in place for seven to eight days. Fractures of the os penis are treated by passing a urinary diversion catheter, suturing it to the prepuce, and incorporating the catheter into a body bandage. If this is not possible, or if late stricture of the penile urethra occurs, a permanent prescrotal urethrostomy is then performed. Intrapelvic Urethra. A ruptured intrapelvic urethra may occur when a male dog is injured in an automotive accident. It is commonly associated with a fractured pelvis. Rupture of the intrapelvic urethra with some mucosal coi_Itinuity and without impingement by a fracture fragment is treated conservatively by inserting a large urinary diversion catheter. The largest size Foley catheter that will easily pass through the urethra is inserted with the aid of ftouroscopy or radiography. When a retrograde passage is not possible, a ventral midline approach for cystotomy and reflection of the fracture fragments may allow passage of the catheter across the rupture possibly under direct vision. If excessive urine is leaking into the tissues after placement of this catheter, it is possible that a larger catheter may be necessary. This replacement should be done with extreme caution for it is possible that the larger catheter may not pass retrogradely, thereby necessitating cystotomy and antegrade passage through the urethra, passing through a permanent prescrotal urethrostomy. If a fracture fragment does impinge on the urethra, it can be repositioned through a ventral approach. The urethral wound is approximated with 4-0 chromic catgut leaving a l to 2 mm gap. Reduction and stabilization of the pelvic fracture fragments can usually be accomplished with wiring techniques. In a few incidences, reduction and
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fixation of total pelvic collapse should be accomplished through a lateral approach to the pelvis and plating the iliac fracture or acetabular fracture. In general a large transurethral urinary diversion catheter is placed without open surgery if possible. The intrapelvic urethra may be approached through a midline symphysiotomy incision or by cutting the pubic bone on both sides of the midline in combination with transverse sectioning of the symphysis pelvis. Surgical approach and suturing of the intrapelvic urethra are done only in those patients in whom urinary diversion catheterization cannot be accomplished by conservative methods. The severed intrapelvic urethra should be anastomosed through the symphysiotomy approach. One to 2 mm of the severed urethral ends should be debrided. A primary anastomosis is made with six simple interrupted silk or chromic catgut sutures using the 180 degrees stay suture method. Prostatovesicular traction, necessary to minimize tension on the sutures, is achieved by placing a wire suture from a urethral splint (large Foley catheter) over two perineal buttons (Fig. 2). The urethral splint is removed 21 days following the operation. A penicillin-streptomycin combination is given intramuscularly for five days following the operation at which time acetyl sulfasoxazole (Lipogantrisin) is used twice a day, or sulfisoxazole (Gantrisin) four times daily until removal of the splint. In an experimental group of animals treated by this method, there was no evidence of separation of the anastomosis of the urethra. Transection of the urethra causes an immediate retraction of the severed urethral ends up into a sleeve of periurethral tissue. Unless the mucosa and muscularis are coapted with sutures over prostatovesicular traction, the mucosa separates. The gap fills with fibrous tissu.e which later contracts into a scar, becoming a stricture.
Subcutaneous traction button
Steel cylinder
Abdominal wall
Figure 2. Anastomosis of the severed intrapelvic urethra. (Modified from MacRoberts, J. W., and Ragde, H.: The severed canine posterior urethra: Study of two distinct methods of repair.]. Urol., 104:724-728, 1970.)
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CHRONIC STRICTURES The signs of anuria or dysuria depend upon the degree and duration of chronic strictures, and can result in other urinary tract changes (retention uropathy) such as urethral dilatation, hydroureter, and hydronephrosis. Futhermore urinary retention can cause crystal formation and infection. In these cases, the entire urinary system should be evaluated by intravenous pyelogram plus contrast cystourethrogram. Common to most patients with chronic strictures is some previous trauma. Chronic blockage of the urethra in the area of the penis is best managed by permanent prescrotal urethrostomy. Temporary urethrotomies that have healed by granulation account for a number of strictures in the prescrotal region. The latter condition is treated by castration and scrotal urethrostomy. Scrotal urethrostomy is preferred over perineal urethrostomy because it obviates the problems of urine spillage and scalding of the skin. Chronic stricture of the intrapelvic urethra which results in dysuria is a serious problem necessitating radical measures. One successful technique is extrapelvic anastomosis of the bladder and the extra pelvic urethra (described later). Another method involves partial replacement of the urethra with a silicone prosthesis. One dog given this treatment has functioned well postoperatively for one year and has a normal appearing cystourethrogram. In an experimental study1 a segment of perineal urethra 2 to 4 mm long was excised except for a small strip of mucosa that bridged the excised gap from one segment of the urethra to the other, thereby maintaining continuity. This small strip appeared to be quite important. A Silastic tube with a Darcon mesh cuff bonded to each end was anastomosed to the cut edges of the urethra with 4-0 chromic catgut continuous sutures. In three dogs a 10 F. prosthesis 2 em in length was used. In another two dogs, a 15 F. prosthesis 4 em in length was used. In the three dogs with the smaller prothesis fistulas, strictures, and displacement of the prosthesis occurred. In the three dogs in which the larger prosthesis was used, urinary function was excellent lasting up to one year in one of these dogs.
EXTRAPELVIC CYSTOURETHRAL ANASTOMOSIS Extrapelvic cystourethral anastomosis3 has been used when chronic stricture of the intrapelvic urethra was diagnosed by a retrograde cystourethogram (Fig. 3). A ventral paramedian skin incision is made in the cranial end of the prepuce and extends caudally just lateral to the scrotum alongside the perineal urethra to just below the anus. The prepuce and penis are reflected laterally and a ventral midline incision
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Penis
B
Figure 3. Extrapelvic cystourethral anastomosis. (Figure 3A is modified from Knecht, C. D., and Slusher, R.: Extrapelvic cystourethral anastomosis. J.A.A.H.A., 6:247-251, 1970.)
is made through the abdominal musculature to the pelvic symphysis. The pelvic urethra is incised caudal to the prostate gland. A transurethral prostatectomy is then performed leaving the neck of the bladder and cystic arteries intact. Care should be taken to dissect the prostate gland off the neck of the bladder, leaving as much of the bladder neck as possible. In the caudal part of the incision, the urethra is incised just proximal to its bulb, severing the bulbocavernous and the retractor penis muscles at an angle. The artery and vein of the bulb are ligated and severed. The dorsal artery of the penis is carefully preserved. The bulb of the urethra is carried cranially, ventral to the pelvis up through the abdominal incision, and anastomosed to the neck of the bladder with eight preplaced, circumferential, simple interrupted 3-0 catgut or surgical nylon sutures, being careful to place at least four throws, (a square knot on top of a surgeon's knot). Also 3-0 Dexon has been used, taking care to apply a surgeon's knot on top of a square knot (four throws). The length of extrapelvic urethra is critical. If it is too short, a sharp bend results just posterior to the os penis. Both testicles can be removed. A urinary diversion catheter is left in place for
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three to four days. Although this procedure seems to be complicated, nonetheless, it is certainly one successful method of handling the serious problem of chronic stricture of the intrapelvic urethra.
URETHRAL OBSTRUCTION Obstruction of the urethra in male dogs is a result of a number of causes, but most commonly, calculi. Strictures resulting from traumatic injuries and previous surgery can result in partial or total obstruction. However the problem they present numerically is usually minor in comparison with the multitude of difficulties caused by urinary calculi. Follow-up medical care is important and must certainly extend beyond surgical intervention and removal of the calculi. It is quite important to prevent the subsequent formation of calculi if possible. Once the diagnosis of urethral obstruction has been made and delineated (by contrast urethrography if possible), a decision must be made as to the best method of management. The management of strictures has been previously discussed. When calculi are the cause of the strictures the following method is used:
Treatment When calculi are determined to be present, an immediate attempt is made to relieve the obstruction. In total obstruction it is important to anesthetize the animal and then to attempt to back flush the urethral calculi into the bladder. It is necessary not to force the catheter because this kind of trauma in a diseased edematous urethra may cause rupture. To dislodge the .calculi, the largest lubricated ureteral (Rusch) catheter is advanced by the surgeon while an assistant forces saline under pressure through the catheter. Occasionally a calculus lodged caudal to the os penis can be crushed with an alligator type forceps, although this should be done with caution to avoid traumatizing the urethral mucosa with the alligator jaw. The remaining calculi are flushed back into the bladder.
Urethrotomy Occasionally the calculi cannot be dislodged by retrograde flushing and an urethrotomy is indicated. A voiding urethrotomy is preferable because of the possibility of stricture formation in the urethra when allowed to heal by granulation. Nonetheless this procedure is necessary in some instances. Prior to the time of surgery, a complete blood count and SMA 12 should be determined and postrenal uremia assessed. Plain and contrast radiographs of the urethra are necessary to determine the location and amount of calculi. The most common site of obstruction is the base of the os penis. Obstruction here often requires surgical inter-
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vention. Uncommonly a urethrotomy in the perineal area will be required, but in most instances the calculus can be removed through a prepubic urethrotomy and by flushing, or occasionally by alligator forceps delivery. Prepubic Urethrotomy
Under general inhalation anesthesia, the patient is placed in dorsal recumbency with the rear legs posterior. The posterior ventral abdomen and prepuce are clipped and prepared aseptically as is the preputial diverticulum. A well lubricated urethral catheter is inserted into the penile urethra to the point of obstruction. A 2 em ventral midline skin incision is made in the caudal prepuce over the site of obstruction, just caudal to the os penis and 2 em cranial to the scrotum. The penis is then grasped between the surgeon's thumb and forefinger to facilitate dissection of the urethra. The subcutis is incised sharply down to theretractor penis muscle as near the midline as possible. The retractor penis muscle is identified, isolated, and retracted laterally. The ventral urethra is seen surrounded by corpus cavernoslJm urethrae. An incision is made into the ventral urethral lumen over the calculi or catheter and extended 1 to 2 em in length. As many calculi as possible are flushed retrogradely into the bladder as the catheter is advanced while flushing under pressure. Some amount of controversy exists as to whether to suture the urethrotomy, converting it to a permanent urethrostomy. If the wound is left open, urine will escape from the wound for a few days, the wound heals by granulation, and in many instances continuity of the urethra is reestablished.
URETHROSTOMY A urethrostomy is the surgical creation of a permanent exterior opening in the urethra. In the male, three types of urethrostomies are performed- prepubic, scrotal, and perineal. It is preferable to avoid urethrotomy and perform a urethrostomy whenever possible because of the numerous complications that can occur. Urethrostomies are recommended under the following circumstances: (1) removal of urethral calculi that cannot be flushed retrogradely; (2) strictures of the penile urethra resulting from previous incisions or traumatic injuries; (3) facilitates passage of urethral stones in dogs in which rapid stone formation cannot be controlled medically; and (4) penis amputation for carcinoma, or other malignancy. As previously stated, urethrostomy rather than urethrotomy is preferred to avoid possible urethral strictures.
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Prepubic Urethrostomy This surgical procedure is often performed to relieve obstruction resulting from calculi when other means fail. If obstruction occurs at the ischial arch, a prepubic urethrostomy is performed and the calculi can sometimes be removed by flushing or by grasping with an alligator forceps. The same procedure as previously described is used for prepubic urethrostomy. After removal of the calculi and urethral irrigation, the urethral mucosa is sutured with 4-0 or 5-0 nylon sutures in a simple interrupted pattern through the incised urethral mucosa, corpus cavernosum urethrae, and skin. The urethrostomy opening should be approximately l 1/2 to 2 em in length. One suture in the posterior aspect of the incision should be placed to create a round opening and to prevent the skin from growing over the urethrostomy site. Bleeding from the corpus cavernosum may be profuse but can be controlled with epinephrine soaked sponges and slightly deeper placement of the sutures into the urethra or the use of synthetic estrogens. Scrotal Urethrostomy Scrotal urethrostomy is performed in animals with obstruction cranial to the scrotum from any cause. Some have recommended this procedure be carried out in animals that are rapid stone formers when medical treatment is ineffective. It has been advocated to prevent numerous urethrotomies in rapid stone formers because the calculi are able to pass through the'larger scrotal urethrostomy and not lodge at the os penis. Advantages of the scrotal urethrostomy are as follows: l. The urethra is more superfical at the scrotum than elsewhere and therefore this type of surgery is a little less difficult to perform than a urethrostomy. 2. The urethra is surrounded by less cavernous tissue at the scrotum and therefore less hemorrhage occurs. The urethra is wide at the scrotum so that the stones pass through this opening slightly more readily than in prepubic urethrotomy. Surgical Technique Under general inhalation anesthesia, the dog is placed in dorsal recumbency and the legs secured posteriorly. The scrotum and surrounding tissues are clipped and prepared aseptically for surgery. A skin incision is made around the circumference of the scrotum at its midequatorial point. The incision should be made on the lateral aspect to allow enough skin for .suturing to the urethral mucosa without extensive tension on the sutures. The excessive scrotal skin can be removed later if necessary. A routine castration is then performed. After castration, the connective tissue overlying the urethra can be incised and the retractor penis muscle identified and retracted laterally.
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Reflection of this muscle laterally exposes the ventral urethra that visually is a white glistening band of tissue between two bands of cavernous tissue. The urethra is incised 3 to 4 em from its ventral most portion to the dorsal curve (to the beginning of the urethral arch). The urethral mucosa appears as pink glistening membrane. Two stay sutures are placed on the lateral urethral edges. Suturing the urethrostomy incision begins with the posterior urethral incision to insure an adequte caudal round opening of the urethra. The lateral skin edges are sutured to the urethra with 4-0 or 5-0 nylon sutures (Ethilon) in a simple interrupted pattern. Only a small amount of skin and urethral mucosa should be included with each suture. As stated as before, excessive scrotal skin may be removed. When suturing the urethrostomy incision, tension on the sutures should be carefully avoided. In some instances, where there has been excessive hemorrhage, swelling occurs necessitating the placement of a urinary catheter for a few days in combination with an Elizabethan collar. Perineal Urethrostomy
Perineal urethrostomy should be performed in the dog only if no other method is possible because of urine spillage and burning of the skin. Under general inhalation anesthetic a catheter is placed into the urethra as far as possible. The patient is placed in a perineal position and prepared for surgery. A purse-string suture is placed in the anus prior to scrubbing to prevent caudal extrusion of fecal material. The skin incision is made on the midline approximateiy 2 to 3 em dorsal to the scrotum. The subcutaneous tissue over the urethra, which lies deep on the midline surrounded by bulbocavernous muscle, is incised. The urethra can be identified by palpation of the catheter. The urethra and surrounding cavernous tissue are moved to the incision by gentle manipulation with an Allis forceps or stay sutures. Fibers of the bulbocavernous muscle are separated longitudinally over the catheter and the urethra incised over the catheter. Sutures of simple interrupted 4-0 nylon are placed in the urethral mucosa and edge of the skin to create a permanent opening. Postoperative Care
A cystotomy must be performed after urethrotomies (urethrostomies) if calculi were flushed into or are in the bladder. All urethrostomies are managed basically the same. An Elizabethan collar, urinary antibiotics, and tranquilizers are given as necessary. In some instances an antibiotic-steroid ointment is applied to the wound if excessive inflammation is present. Most importantly, follow-up therapy to prevent calculi formation is given. Therefore at the time of cystotomy, it is most important to retrieve calculi for chemical analysis and to culture the wall of the urinary bladder to identify any pathogenic bacteria.
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Complications
Complications can be numerous following urethrotomies and urethrostomies. If the procedure is improperly performed, urine may extravasate into periurethral tissues creating pitting edema and inflammation. When this occurs, an indwelling catheter should be inserted and left in place for three to five days. Hemorrhage occurring for as long as l 0 days can be common. Systemic tranquilizers and synthetic estrogens will help to control such bleeding. Strictures resulting from previous surgeries are always a problem. When they do occur, another type of correctly performed urethrostomy is indicated. The surgeon should not hesitate to learn the correct method and perform it.
REFERENCES l. Gilbaugh,]. H., Utz, D. C., and Walkim K. G.: Partial replacement of the canine
urethra with silicone prosthesis. Invest. Urol., 7:41, I 969. 2. Hobson, H. P., and Heller, P. A.: Surgical correction of the prolapsed male urethra. Vet. Med., 1177, I 971. 3. Knecht, C. D., and Slusher, R.: Extrapelvic cystourethral anastomosis ..J.A.A.H.A., 6:247-251, 1970. 4. MacRoberts, .J. W., and Ragde, H.: The severed canine posterior urethra: Study of two distinct methods of repair. J. Urol., 104:724, I 970. 5. Weaver, R. G., and Shultie,]. W.: Experimental and clinical studies of urethral regeneration. Surg. Gynecol. Obstet., 115:729, 1972. Berkeley Veterinary Medical Group 800 University Avenue Berkeley, California 94710
Surgery of the Canine Urethra S. Gary Brown, D.V.M.*
ANATOMY The urethra serves a dual role both as a conduit for urine from the bladder to the outside and as a purveyor of seminal fluids. The first segment of the urethra is the prostatic urethra. This is followed by the membranous or intrapelvic urethra which extends from the caudal end of the prostate to the bulb of the penis that is superior to the caudal pelvic symphisis. Third, the extrapelvic or cavernous urethra begins at the bulb of the penis and extends to its tip. The urethra is a highly distensible organ whose diameter is slightly variable throughout, except at the caudal os penis where the bony os limits the urethra's ability to expand. This is a common area for urethral calculi to lodge. The entire urethra is lined with transitional epithelium with the exception of a small amount near the tip of the penis. Urethral muscle is composed of an inner longitudinal layer of smooth muscle ~nd aN outer transverse layer of skeletal muscle that are separated dorsally by a longitudinal connective tissue raphe. The prostatic urethra is supplied by the prostatic branch of the urogenital artery. The membranous or intrapelvic urethra receives most of the supply from the smaller urethral arteries. The extrapelvic or penile urethra is supplied by the artery of the urethral bulb. Venous drainage of the urethra flows into the internal pudendal vein. Autonomic nerves from the pelvic plexus supply the smooth muscle of the urethra. Voluntary control of urethral muscle is mediated by the pudenal nerve. The female urethra traverses caudally from the neck of the bladder and enters the floor of the vagina just slightly caudal to the junction between the vaginal and vestibular floor. The urethra opens on the urethral tubercle just cranial to the lips of the vulva. *Surgeon: Berkeley Veterinary Medica]. Group, Berkeley, California; Clinical Assistant Professor, Department of Clinical Sciences. College of Veterinary Medicine, University of California at Davis Veterinary Clinics of North America- Vol. 5, No. 3, August 1975
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CONGENITAL ANOMALIES
These rare conditions can often be diagnosed by physical examination. Urethral duplications, atresia, and diverticula can occur however, and are best confirmed by contrast cystourethrography. Hypospadias and epispadias usually occur with other congenital malformations. In hypospadias, the urethral opening is anywhere on the ventral surface although it is usually on the penis or the ventral glans penis shaft. In epispadias, the urethral orifice is on the upper surface of the penis somewhere caudal to the tip. URETHRAL PROLAPSE
Prolapse of the penile urethra, an infrequent occurrence, usually requires surgical treatment. It occurs most often in young brachiocephalic dogs such as Boston terriers and English bulldogs. Prolonged sexual excitement (real or imagined), urethral infection, and congenital abnormalities are probably the cause of this condition, although the exact etiopathogenesis is not fully understood. The diagnosis is based on history and clinical signs. Excessive licking of the tip of the penis and preputial orifice with noticeable hemorrhage from the prepuce suggests the possibility of this lesion. This is confirmed by direct observation of the mucosa protruding from the tip of the penis. Although the color and size of the prolapse vary, the mucosa is usually brig~t red to purple and donut shaped as it pushes forth to extend beyond and around the tip of the penis. Surgical Treatment
Under general anesthesia with nitrous oxide- oxygen (2 to 1) in halothane- the dog is placed in dorsal recumbency. The prepuce and surrounding abdomen are clipped and prepared aseptically for surgery. The preputial diverticulum and penis are irrigated with an antiseptic solution prior to scrubbing and draping the operative area. When the prolapse is small, and is not grossly engorged with blood, a conservative repair is preferred. The penis is extended from the sheath and grasped between the thumb and forefinger. A well lubricated catheter of the largest diameter that will pass easily is introduced into the urethral orifice while reduction of the prolapse is attempted. If the prolapse has been reduced the catheter is then placed into the bladder and a purse-string suture of 3-0 or 4-0 nylon is placed around the tip of the penis. The catheter is then sutured to the prepuce to maintain its position in the urethra and bladder for five to seven days. In some dogs, it is wise to add an Elizabethan collar at this point whereas in others it is unnecessary.
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0
E
Figure 1.
Surgical correction of urethral prolapse.
If the prolapse is severe and obviously nonreducible, amputation of the diseased tissue in the prolapsed segment is preferred. As with the preparation previously described the penis is grasped and a well lubricated catheter is inserted through the urethra into the bladder. Four stay sutures are placed equidistant around the tip of the penis through the urethral mucosa to prevent the inner mucosa from retracting (Fig. 1). The prolapse is excised over the catheter as close to the penis as possible. Simple interrupted sutures of 4-0 to 5-0 chromic catgut are placed around the tip of the penis approximately 2 to 4 mm apart uniting the urethral mucosa to the cranial tip of the penis. The catheter is sutured to the prepuce to maintain its position for four days. Postoperative Care
A urinary antibiotic such as sulfisoxazole (Gantrisin), acetylsulfafurazole (Lipogantrisin), chloramphenicol (Chloromycetin), or· genta-
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micin (Gentocin) should be used to control infection. A tranquilizer such as acepromazine has been quite beneficial. Here again, an Elizabethan collar is helpful to prevent catheter removal and licking at the operative site. If possible the urinary catheter is drained through a long polyethylene tube into a clean bottle to prevent retrograde contamination.
Complications Self-mutilation can be controlled as previously mentioned and postoperative bleeding can usually be arrested with synthetic estrogens or tranquilizers.
ACUTE URETHRAL TRAUMA Etiology Acute urethral trauma is often the result of catheterization of a urethra already edematous from the presence of disease or more often urethral calculi. Urethral calculi themselves, in fact, cause urethral trauma. Direct injury may be either a sharp laceration or blunt injury causing bruising and edema of the urethra and surrounding tissues. Because of its tearing nature, biting injuries of the urethra damage the tissue more extensively than does a sharp laceration; bite wounds increase the possibility of infection. Surgical damage to the female urethra can occur during resection of a vaginal tumor or vaginal prolapse if the female urethra has not been catheterized. In the male, injury to the tip of the penis has been reported following sexual activity that has resulted in the prolapsed urethra. Fracture of the os penis with attendant urethral injury occurs rarely in the dog.
Diagnosis Diagnosis is generally based on history, physical examination, catheterization, and plain film plus contrast urethrography. All trauma patients with hematuria should have close inspection of urinary systems. Contrast cystourethrograms or intravenous pyelograms are invaluable.
Complications The traumatized or lacerated urethra can result in strictures and dysuria. Urethral dilatation and other secondary disease (retention uropathy) of the urinary system, cranial to the lesion, can also occur. Leakage through a rupture may cause infiltration of the surrounding tissues with urine that can then progress to secondary edema and swelling of the scrotum and the rear limbs. Chronic urine retention from strictures can result in urinary tract infection, crystal formation, and hydrodilatations. Complete retention from strictures and ruptures result in anuria and uremia.
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Treatment
Extrapelvic Urethra. Bruising of the urethra and periurethra can be seen as a segmental narrowing of the dye stream in a cystourethrogram. If the urethra is intact, the injury is treated conservatively with urinary antibiotics, hot packs, and tranquilizers. If the urethra is intact and the tissues in the area are markedly bruised, manual expression or placement of a urinary diversion catheter, sutured to the prepuce, may be necessary for several days. Lacerations of the external urethra should be surgically treated before the urine extravasates into the surrounding tissues and causes edema. The edges of the laceration are approximated with sutures over a previously passed transurethral Foley or Brunswick catheter of the largest size that can be comfortably passed by the os penis into the bladder. If the laceration has been sharp, producing minimal tissue damage, the edges are approximated with simple interrupted 4-0 chromic catgut placed 2 mm apart, leaving a gap of 2mm between the urethral wound edges. This method of edge approximation over a catheter has been used to circumvent an unacceptable number of strictures resulting from primary water tight closures. If the rupture has occurred in a urethra that is already edematous, possibly from calculi, it is probably better to do a permanent prescrotal urethrostomy first so that then one would be able to pass a slighty larger Foley catheter to do the previous repair of the external urethra. This permanent urethrostomy will then be useful for the passage of future small stones. Suturing the external part of the catheter to the prepuce and/or incorporating this into a body bandage will prevent the dog from removing the catheter. This catheter should rema~n in place for seven to ten days. These extra precautions are desirable since reinsertion of the catheter may disrupt the sutured area of the urethra. If one expects a more chronic catheterization for any reason the catheter can be placed through a prescrotal permanent urethrostomy and sutured to the skin. For example, in more severe injuries where a loss of urethral tissue is creating a large defect or other massive disruption to the urethra, a large Foley catheter is passed through the prescrotal urethrostomy past the injury and into the bladder. One inch is allowed to protrude and sutured into the skin edge. The torn edges are approximated over the catheter by simple interrupted sutures of 4-0 chromic catgut with a gap of 2 mm always being left. It the edges are approximated over a large defect, there should be no tension on the sutures. The catheter may remain in place for two to three weeks as long as urinary antibiotics are being administered. Bite wounds of the urethra may be treated in like fashion, remembering that extensive damage predisposes to infection and therefore the wound is closed over a Penrose drain. If gross infection is present the external wound is debrided if necessary and dressed with antibiot-
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ics for two days while urinary diversion is maintained through a catheter. The dressing may be sutured directly to the skin. After two days the urethra and granulating tissue are closed over the catheter as described using a Penrose drain. Some mucosal continuity is desired for healing. In experimental and clinical studies of the anterior urethra, it has been demonstrated that regeneration of the urethra, including the corpus and corpus spongiosum, is possible provided that the urethra does not have to bridge an area of complete excision. This is important to remember when chronic catheterization is used for urethral defects. A severed urethra should be repaired as soon as possible. The ends of the severed urethra are debrided l to 2 mm prior to the anastomosis. Stay sutures are placed 180 degrees apart to position the anastomosis. The anastomosis is then completed with six to eight interrupted sutures of 4-0 chromic catgut placed circumferentially to bring together the mucosal and muscularis layers. The bottom layer is closed first and the layer closest to the surgeon (outer) is closed last over a Foley urinary diversion catheter. This is left in place for seven to eight days. Fractures of the os penis are treated by passing a urinary diversion catheter, suturing it to the prepuce, and incorporating the catheter into a body bandage. If this is not possible, or if late stricture of the penile urethra occurs, a permanent prescrotal urethrostomy is then performed. Intrapelvic Urethra. A ruptured intrapelvic urethra may occur when a male dog is injured in an automotive accident. It is commonly associated with a fractured pelvis. Rupture of the intrapelvic urethra with some mucosal coi_Itinuity and without impingement by a fracture fragment is treated conservatively by inserting a large urinary diversion catheter. The largest size Foley catheter that will easily pass through the urethra is inserted with the aid of ftouroscopy or radiography. When a retrograde passage is not possible, a ventral midline approach for cystotomy and reflection of the fracture fragments may allow passage of the catheter across the rupture possibly under direct vision. If excessive urine is leaking into the tissues after placement of this catheter, it is possible that a larger catheter may be necessary. This replacement should be done with extreme caution for it is possible that the larger catheter may not pass retrogradely, thereby necessitating cystotomy and antegrade passage through the urethra, passing through a permanent prescrotal urethrostomy. If a fracture fragment does impinge on the urethra, it can be repositioned through a ventral approach. The urethral wound is approximated with 4-0 chromic catgut leaving a l to 2 mm gap. Reduction and stabilization of the pelvic fracture fragments can usually be accomplished with wiring techniques. In a few incidences, reduction and
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fixation of total pelvic collapse should be accomplished through a lateral approach to the pelvis and plating the iliac fracture or acetabular fracture. In general a large transurethral urinary diversion catheter is placed without open surgery if possible. The intrapelvic urethra may be approached through a midline symphysiotomy incision or by cutting the pubic bone on both sides of the midline in combination with transverse sectioning of the symphysis pelvis. Surgical approach and suturing of the intrapelvic urethra are done only in those patients in whom urinary diversion catheterization cannot be accomplished by conservative methods. The severed intrapelvic urethra should be anastomosed through the symphysiotomy approach. One to 2 mm of the severed urethral ends should be debrided. A primary anastomosis is made with six simple interrupted silk or chromic catgut sutures using the 180 degrees stay suture method. Prostatovesicular traction, necessary to minimize tension on the sutures, is achieved by placing a wire suture from a urethral splint (large Foley catheter) over two perineal buttons (Fig. 2). The urethral splint is removed 21 days following the operation. A penicillin-streptomycin combination is given intramuscularly for five days following the operation at which time acetyl sulfasoxazole (Lipogantrisin) is used twice a day, or sulfisoxazole (Gantrisin) four times daily until removal of the splint. In an experimental group of animals treated by this method, there was no evidence of separation of the anastomosis of the urethra. Transection of the urethra causes an immediate retraction of the severed urethral ends up into a sleeve of periurethral tissue. Unless the mucosa and muscularis are coapted with sutures over prostatovesicular traction, the mucosa separates. The gap fills with fibrous tissu.e which later contracts into a scar, becoming a stricture.
Subcutaneous traction button
Steel cylinder
Abdominal wall
Figure 2. Anastomosis of the severed intrapelvic urethra. (Modified from MacRoberts, J. W., and Ragde, H.: The severed canine posterior urethra: Study of two distinct methods of repair.]. Urol., 104:724-728, 1970.)
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CHRONIC STRICTURES The signs of anuria or dysuria depend upon the degree and duration of chronic strictures, and can result in other urinary tract changes (retention uropathy) such as urethral dilatation, hydroureter, and hydronephrosis. Futhermore urinary retention can cause crystal formation and infection. In these cases, the entire urinary system should be evaluated by intravenous pyelogram plus contrast cystourethrogram. Common to most patients with chronic strictures is some previous trauma. Chronic blockage of the urethra in the area of the penis is best managed by permanent prescrotal urethrostomy. Temporary urethrotomies that have healed by granulation account for a number of strictures in the prescrotal region. The latter condition is treated by castration and scrotal urethrostomy. Scrotal urethrostomy is preferred over perineal urethrostomy because it obviates the problems of urine spillage and scalding of the skin. Chronic stricture of the intrapelvic urethra which results in dysuria is a serious problem necessitating radical measures. One successful technique is extrapelvic anastomosis of the bladder and the extra pelvic urethra (described later). Another method involves partial replacement of the urethra with a silicone prosthesis. One dog given this treatment has functioned well postoperatively for one year and has a normal appearing cystourethrogram. In an experimental study1 a segment of perineal urethra 2 to 4 mm long was excised except for a small strip of mucosa that bridged the excised gap from one segment of the urethra to the other, thereby maintaining continuity. This small strip appeared to be quite important. A Silastic tube with a Darcon mesh cuff bonded to each end was anastomosed to the cut edges of the urethra with 4-0 chromic catgut continuous sutures. In three dogs a 10 F. prosthesis 2 em in length was used. In another two dogs, a 15 F. prosthesis 4 em in length was used. In the three dogs with the smaller prothesis fistulas, strictures, and displacement of the prosthesis occurred. In the three dogs in which the larger prosthesis was used, urinary function was excellent lasting up to one year in one of these dogs.
EXTRAPELVIC CYSTOURETHRAL ANASTOMOSIS Extrapelvic cystourethral anastomosis3 has been used when chronic stricture of the intrapelvic urethra was diagnosed by a retrograde cystourethogram (Fig. 3). A ventral paramedian skin incision is made in the cranial end of the prepuce and extends caudally just lateral to the scrotum alongside the perineal urethra to just below the anus. The prepuce and penis are reflected laterally and a ventral midline incision
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Penis
B
Figure 3. Extrapelvic cystourethral anastomosis. (Figure 3A is modified from Knecht, C. D., and Slusher, R.: Extrapelvic cystourethral anastomosis. J.A.A.H.A., 6:247-251, 1970.)
is made through the abdominal musculature to the pelvic symphysis. The pelvic urethra is incised caudal to the prostate gland. A transurethral prostatectomy is then performed leaving the neck of the bladder and cystic arteries intact. Care should be taken to dissect the prostate gland off the neck of the bladder, leaving as much of the bladder neck as possible. In the caudal part of the incision, the urethra is incised just proximal to its bulb, severing the bulbocavernous and the retractor penis muscles at an angle. The artery and vein of the bulb are ligated and severed. The dorsal artery of the penis is carefully preserved. The bulb of the urethra is carried cranially, ventral to the pelvis up through the abdominal incision, and anastomosed to the neck of the bladder with eight preplaced, circumferential, simple interrupted 3-0 catgut or surgical nylon sutures, being careful to place at least four throws, (a square knot on top of a surgeon's knot). Also 3-0 Dexon has been used, taking care to apply a surgeon's knot on top of a square knot (four throws). The length of extrapelvic urethra is critical. If it is too short, a sharp bend results just posterior to the os penis. Both testicles can be removed. A urinary diversion catheter is left in place for
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three to four days. Although this procedure seems to be complicated, nonetheless, it is certainly one successful method of handling the serious problem of chronic stricture of the intrapelvic urethra.
URETHRAL OBSTRUCTION Obstruction of the urethra in male dogs is a result of a number of causes, but most commonly, calculi. Strictures resulting from traumatic injuries and previous surgery can result in partial or total obstruction. However the problem they present numerically is usually minor in comparison with the multitude of difficulties caused by urinary calculi. Follow-up medical care is important and must certainly extend beyond surgical intervention and removal of the calculi. It is quite important to prevent the subsequent formation of calculi if possible. Once the diagnosis of urethral obstruction has been made and delineated (by contrast urethrography if possible), a decision must be made as to the best method of management. The management of strictures has been previously discussed. When calculi are the cause of the strictures the following method is used:
Treatment When calculi are determined to be present, an immediate attempt is made to relieve the obstruction. In total obstruction it is important to anesthetize the animal and then to attempt to back flush the urethral calculi into the bladder. It is necessary not to force the catheter because this kind of trauma in a diseased edematous urethra may cause rupture. To dislodge the .calculi, the largest lubricated ureteral (Rusch) catheter is advanced by the surgeon while an assistant forces saline under pressure through the catheter. Occasionally a calculus lodged caudal to the os penis can be crushed with an alligator type forceps, although this should be done with caution to avoid traumatizing the urethral mucosa with the alligator jaw. The remaining calculi are flushed back into the bladder.
Urethrotomy Occasionally the calculi cannot be dislodged by retrograde flushing and an urethrotomy is indicated. A voiding urethrotomy is preferable because of the possibility of stricture formation in the urethra when allowed to heal by granulation. Nonetheless this procedure is necessary in some instances. Prior to the time of surgery, a complete blood count and SMA 12 should be determined and postrenal uremia assessed. Plain and contrast radiographs of the urethra are necessary to determine the location and amount of calculi. The most common site of obstruction is the base of the os penis. Obstruction here often requires surgical inter-
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vention. Uncommonly a urethrotomy in the perineal area will be required, but in most instances the calculus can be removed through a prepubic urethrotomy and by flushing, or occasionally by alligator forceps delivery. Prepubic Urethrotomy
Under general inhalation anesthesia, the patient is placed in dorsal recumbency with the rear legs posterior. The posterior ventral abdomen and prepuce are clipped and prepared aseptically as is the preputial diverticulum. A well lubricated urethral catheter is inserted into the penile urethra to the point of obstruction. A 2 em ventral midline skin incision is made in the caudal prepuce over the site of obstruction, just caudal to the os penis and 2 em cranial to the scrotum. The penis is then grasped between the surgeon's thumb and forefinger to facilitate dissection of the urethra. The subcutis is incised sharply down to theretractor penis muscle as near the midline as possible. The retractor penis muscle is identified, isolated, and retracted laterally. The ventral urethra is seen surrounded by corpus cavernoslJm urethrae. An incision is made into the ventral urethral lumen over the calculi or catheter and extended 1 to 2 em in length. As many calculi as possible are flushed retrogradely into the bladder as the catheter is advanced while flushing under pressure. Some amount of controversy exists as to whether to suture the urethrotomy, converting it to a permanent urethrostomy. If the wound is left open, urine will escape from the wound for a few days, the wound heals by granulation, and in many instances continuity of the urethra is reestablished.
URETHROSTOMY A urethrostomy is the surgical creation of a permanent exterior opening in the urethra. In the male, three types of urethrostomies are performed- prepubic, scrotal, and perineal. It is preferable to avoid urethrotomy and perform a urethrostomy whenever possible because of the numerous complications that can occur. Urethrostomies are recommended under the following circumstances: (1) removal of urethral calculi that cannot be flushed retrogradely; (2) strictures of the penile urethra resulting from previous incisions or traumatic injuries; (3) facilitates passage of urethral stones in dogs in which rapid stone formation cannot be controlled medically; and (4) penis amputation for carcinoma, or other malignancy. As previously stated, urethrostomy rather than urethrotomy is preferred to avoid possible urethral strictures.
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Prepubic Urethrostomy This surgical procedure is often performed to relieve obstruction resulting from calculi when other means fail. If obstruction occurs at the ischial arch, a prepubic urethrostomy is performed and the calculi can sometimes be removed by flushing or by grasping with an alligator forceps. The same procedure as previously described is used for prepubic urethrostomy. After removal of the calculi and urethral irrigation, the urethral mucosa is sutured with 4-0 or 5-0 nylon sutures in a simple interrupted pattern through the incised urethral mucosa, corpus cavernosum urethrae, and skin. The urethrostomy opening should be approximately l 1/2 to 2 em in length. One suture in the posterior aspect of the incision should be placed to create a round opening and to prevent the skin from growing over the urethrostomy site. Bleeding from the corpus cavernosum may be profuse but can be controlled with epinephrine soaked sponges and slightly deeper placement of the sutures into the urethra or the use of synthetic estrogens. Scrotal Urethrostomy Scrotal urethrostomy is performed in animals with obstruction cranial to the scrotum from any cause. Some have recommended this procedure be carried out in animals that are rapid stone formers when medical treatment is ineffective. It has been advocated to prevent numerous urethrotomies in rapid stone formers because the calculi are able to pass through the'larger scrotal urethrostomy and not lodge at the os penis. Advantages of the scrotal urethrostomy are as follows: l. The urethra is more superfical at the scrotum than elsewhere and therefore this type of surgery is a little less difficult to perform than a urethrostomy. 2. The urethra is surrounded by less cavernous tissue at the scrotum and therefore less hemorrhage occurs. The urethra is wide at the scrotum so that the stones pass through this opening slightly more readily than in prepubic urethrotomy. Surgical Technique Under general inhalation anesthesia, the dog is placed in dorsal recumbency and the legs secured posteriorly. The scrotum and surrounding tissues are clipped and prepared aseptically for surgery. A skin incision is made around the circumference of the scrotum at its midequatorial point. The incision should be made on the lateral aspect to allow enough skin for .suturing to the urethral mucosa without extensive tension on the sutures. The excessive scrotal skin can be removed later if necessary. A routine castration is then performed. After castration, the connective tissue overlying the urethra can be incised and the retractor penis muscle identified and retracted laterally.
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Reflection of this muscle laterally exposes the ventral urethra that visually is a white glistening band of tissue between two bands of cavernous tissue. The urethra is incised 3 to 4 em from its ventral most portion to the dorsal curve (to the beginning of the urethral arch). The urethral mucosa appears as pink glistening membrane. Two stay sutures are placed on the lateral urethral edges. Suturing the urethrostomy incision begins with the posterior urethral incision to insure an adequte caudal round opening of the urethra. The lateral skin edges are sutured to the urethra with 4-0 or 5-0 nylon sutures (Ethilon) in a simple interrupted pattern. Only a small amount of skin and urethral mucosa should be included with each suture. As stated as before, excessive scrotal skin may be removed. When suturing the urethrostomy incision, tension on the sutures should be carefully avoided. In some instances, where there has been excessive hemorrhage, swelling occurs necessitating the placement of a urinary catheter for a few days in combination with an Elizabethan collar. Perineal Urethrostomy
Perineal urethrostomy should be performed in the dog only if no other method is possible because of urine spillage and burning of the skin. Under general inhalation anesthetic a catheter is placed into the urethra as far as possible. The patient is placed in a perineal position and prepared for surgery. A purse-string suture is placed in the anus prior to scrubbing to prevent caudal extrusion of fecal material. The skin incision is made on the midline approximateiy 2 to 3 em dorsal to the scrotum. The subcutaneous tissue over the urethra, which lies deep on the midline surrounded by bulbocavernous muscle, is incised. The urethra can be identified by palpation of the catheter. The urethra and surrounding cavernous tissue are moved to the incision by gentle manipulation with an Allis forceps or stay sutures. Fibers of the bulbocavernous muscle are separated longitudinally over the catheter and the urethra incised over the catheter. Sutures of simple interrupted 4-0 nylon are placed in the urethral mucosa and edge of the skin to create a permanent opening. Postoperative Care
A cystotomy must be performed after urethrotomies (urethrostomies) if calculi were flushed into or are in the bladder. All urethrostomies are managed basically the same. An Elizabethan collar, urinary antibiotics, and tranquilizers are given as necessary. In some instances an antibiotic-steroid ointment is applied to the wound if excessive inflammation is present. Most importantly, follow-up therapy to prevent calculi formation is given. Therefore at the time of cystotomy, it is most important to retrieve calculi for chemical analysis and to culture the wall of the urinary bladder to identify any pathogenic bacteria.
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Complications
Complications can be numerous following urethrotomies and urethrostomies. If the procedure is improperly performed, urine may extravasate into periurethral tissues creating pitting edema and inflammation. When this occurs, an indwelling catheter should be inserted and left in place for three to five days. Hemorrhage occurring for as long as l 0 days can be common. Systemic tranquilizers and synthetic estrogens will help to control such bleeding. Strictures resulting from previous surgeries are always a problem. When they do occur, another type of correctly performed urethrostomy is indicated. The surgeon should not hesitate to learn the correct method and perform it.
REFERENCES l. Gilbaugh,]. H., Utz, D. C., and Walkim K. G.: Partial replacement of the canine
urethra with silicone prosthesis. Invest. Urol., 7:41, I 969. 2. Hobson, H. P., and Heller, P. A.: Surgical correction of the prolapsed male urethra. Vet. Med., 1177, I 971. 3. Knecht, C. D., and Slusher, R.: Extrapelvic cystourethral anastomosis ..J.A.A.H.A., 6:247-251, 1970. 4. MacRoberts, .J. W., and Ragde, H.: The severed canine posterior urethra: Study of two distinct methods of repair. J. Urol., 104:724, I 970. 5. Weaver, R. G., and Shultie,]. W.: Experimental and clinical studies of urethral regeneration. Surg. Gynecol. Obstet., 115:729, 1972. Berkeley Veterinary Medical Group 800 University Avenue Berkeley, California 94710